Ch 7. Alternating Current Flashcards
The root mean square (r.m.s) value of alternating current of equation I = 60sin 100 π t is
60/√2
For resonance condition in any L-C-R circuit, the phase difference between applied voltage and current is
Zero
The phase difference between current and voltage is only capacitive alternating current circuit is
90•
90 degree
The impedance of L-R circuit is
The impedance of the LR series circuit is Z=√R²+(ωL)²
In step up transformer, the value of current in secondary coil compared to primary coil is
Less
Capacitive reactance is
1/ωC
The relation between r.m.s value of alternating current (I r.m.s) and peak value of alternating current ( I₀ ) is
Neeche r.m.s
I r.m.s. = 0.707I₀
Neeche r.m.s
Inductive reactance offered by an inductor of inductance L in A.C. circuit of angular frequency ω is
ω.L
In an alternating current circuit, the phase difference between current I and voltage is φ then Wattless component of current will be
I sin φ
The ratio of root mean square (r.m.s) value and peak value of an alternating current is
1/√2
In A.C. circuit, the current and voltage are given by i = 5 cos ωt and V = 200 sin ωt respectively. Power loss in the circuit is
Zero
The relation between peak current I₀ and root mean square current I rms is
Neeche rms
I₀ = √2 I rms
Neeche rms
The unit of reactance is
Ohm
Hot wire ammeter measures
r.m.s. value of A.C.
If the equation of an electric current is
I = 0.6 sin 100 πt, the frequency of electric current is
50
The ratio of peak value and r.m.s value of ac is
√2
The peak voltage of an A.C. is 440 volt. its virtual voltage is
220√2 V
In the following Question Nos. 1st to 4th, there are two columns, Column 1st contains 4 questions. You have to match the correct options of these questions as A,B,C and D from column 2nd.
- Frequency of D.C. = Zero
- Choke coil = reduces A.C. current
- Energy density of electric field = 1/2 ε₀ E²
- 1kWh = 3.6 × 10⁶J
Which of the following relations is correct for power factor?
Power factor = True average power/Apparent average power
The power factor of L- R circuit is
R/√R² + ω² L²
Impedance of L-R circuit is
√R² + ω² L²
If φ is the phase difference between A.C. current and e.m.f., then the value of power factor is
Cos φ
Dimensional formula of R.C. is
M⁰L⁰T
The expression for real average power in an alternating current circuit is
P av = E rms I rms cos φ
Neeche av, rms and rms
Power factor is equal to
R/Z
Phase difference in (L-R) circuit is
tan⁻¹ (ωL/R)
Inductive reactance is
X l = 2πfL
Neeche l
Inductive reactance for direct current is
Zero
Which of the following is correct for transformer?
It increases or decreases A.C. voltage
Which quantity decreases in step-down transformer?
Voltage
If N₁ and N₂ are number of primary and secondary coils of a step-up transformer, then
N₂ > N₁
The working of dynamo is based on the principle of
Electromagnetic induction
Transformation ratio in transformer is
V s/V p
S and p neeche
Which of the following is correct for step-up transformer?
V s > V p
S and p neeche
